U.S. Secretary of State John Kerry urged Russia on Monday to meet Ukraine halfway in trying to implement an agreement to defuse the crisis in the former Soviet republic.

Kerry spoke with Russian Foreign Minister Sergei Lavrov by telephone on Monday morning, State Department spokeswoman Jen Psaki said. Russia, Ukraine, the European Union and the United States on Thursday agreed on ways to ease tensions in the worst confrontation between Russia and the West since the Cold War.

“The secretary urged Russia to take concrete steps to help implement the Geneva agreement, including publicly calling on separatists to vacate illegal buildings and checkpoints, accept amnesty and address their grievances politically,” Psaki said at a news briefing.

Lavrov, meanwhile, blamed authorities in Kyiv for the unrest in the Ukraine’s east, calling them “unable or unwilling” to put an end to violence perpetrated by nationalist extremists, a Russian Foreign Ministry statement said.

With pro-Moscow separatists showing no sign of surrendering government buildings they have seized in eastern Ukraine, Washington pegged a threat of new sanctions on Russia to how hard Moscow tries to make the Geneva agreement work.

‘Further costs’ for Moscow

If progress is not made in coming days, we will impose further costs,” White House spokesman Jay Carney said.

The Geneva agreement calls for occupied buildings to be vacated under the auspices of envoys from the Organization for Security and Cooperation in Europe.

Kerry called on Russia to assign a senior diplomat to work with the OSCE mission in eastern Ukraine, Psaki said, “to make absolutely clear to the separatists that Russia supports the agreement and wants de-escalation.”

“The secretary also made clear that Russia's recent public statement casting doubt on Ukraine's commitment to the Geneva agreement flies in the face of the facts,” Psaki said.

Commenting separately on Russia’s accusations, Ukraine’s foreign minister expressed surprise over “Lavrov not being aware of what is happening in Ukraine with regard to the Geneva agreement.”

“We are meeting daily in a quadripartite format, together with the OSCE mission leadership, developing ways of de-escalating the situation in Ukraine’s east,” said Andriy Deshchytsia, according to Ukrainian news agency UNIAN.

He also said he was surprised that Russian diplomats present at these meetings apparently are not reporting back to their Foreign Ministry.

U.S. Vice President Joe Biden is in Ukraine for talks with government officials -- who Russia is claiming "crudely violate" last week's agreement to de-escalate the crisis. VOA State Department Correspondent Scott Stearns reports that agreement to avert wider conflict is faltering -- with pro-Moscow separatist gunmen showing no sign of backing down.

Biden in Ukraine

U.S. Vice President Joe Biden is in Ukraine for talks on the crisis with the acting president and prime minister.

Biden's two-day trip to Kyiv, the highest level visit from a U.S. official since the start of the crisis, was born out of discussions with President Barack Obama, said an administration official briefing reporters on Biden’s plane.

“[Vice President Biden] wanted to come to Kyiv to send a very clear message
of the United States' support for Ukraine's democracy, unity, sovereignty and territorial integrity,” said the official.

A Ukrainian police officer stands guard at a checkpoint that was attacked by unknown men outside the Black Sea port of Odessa, Ukraine, April 25, 2014.

A pro-Russian armed man smokes as he guards near the mayor's office in Slovyansk, Ukraine, April 25, 2014.

A Ukrainian soldier sits atop of his armored vehicle at a check point near the village of Artemiovska, near Slovyansk, Ukraine, April 24, 2014.

Ukrainian security force officers are deployed at a checkpoint set on fire and left by pro-Russian separatists near Slovyansk, April 24, 2014.

A Pro-Russian supporter walks at the seized office of the SBU state security service in Luhansk, eastern Ukraine, April 24, 2014.

Municipal workers take a break from taking down barricades in central Kyiv, April 23, 2014.

Members of Maidan self-defense forces march along the street in central Kyiv, April 23, 2014.

“He will call for urgent implementation of the agreement reached in Geneva last week while also making clear ... that there will be mounting costs for Russia if they choose a destabilizing rather than constructive course in the days ahead,” the official said.

White House officials earlier said Biden will discuss the international community's efforts to help Ukraine move forward on constitutional reform, and for what Obama administration officials say will be a free and fair presidential election on May 25.

In addition, Biden is to announce new economic and energy-related technical assistance for Ukraine during his visit, said an administration official.

Pentagon boosts Europe training

Meanwhile, Pentagon officials are saying that details are being worked out for more training with eastern and central European allies.

Some of the training exercises would be via NATO, others conducted on a bilateral basis, Pentagon officials said at a briefing, adding that all options would "include some level of ground force."

Officials also said that the U.S.is not seeing any substantial troop movements by Russians forces away from Ukraine's border.

Putin decree

Russian President Vladimir Putin signed a decree on Monday to rehabilitate Crimea's Tatars and other minorities who suffered under Soviet dictator Josef Stalin, courting a group that largely opposed Moscow's annexation of the region from Ukraine.

Stalin deported Crimean Tatars to Central Asia en masse during World War Two, accusing them of sympathizing with Nazi Germany, and many died in grueling conditions on arrival in exile.

The Muslim Tatars were allowed to return in the waning days of the Soviet Union, whose 1991 collapse left Crimea in an independent Ukraine. They now make up 12 percent of the Crimea peninsula's mostly ethnic Russian population of 2 million.

Many of them boycotted the March 16 referendum in Crimea, which Russia used as a pretext to annex the peninsula, sparking the biggest crisis in relations between Russia and the West since the Cold War.

OSCE mediator meets separatist leader

The senior mediator from the Organization of Security and Cooperation in Europe in eastern Ukraine held his first talks on Monday with the leader of pro-Russian separatists in the city of Slovyansk, a flashpoint of the crisis.

Mark Etherington told reporters he met the self-declared, separatist mayor, Vyacheslav Ponomaryov, for two hours. He had asked whether Ponomaryov and his group would comply with last week's Geneva accord under which Russia and Ukraine agreed that militants should disarm and vacate occupied public buildings.

Etherington did not say how the separatist leader responded or give further details. He said he also asked about people who had been detained in Slovyansk, including the previous mayor, about reports of maltreatment of the Roma minority and about a gunfight on Sunday in which at least three men were killed.

VOA's Jeff Seldin contributed to this story; some reporting by Reuters

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